Importance of Electrodiagnostic Testing Prior to a Tethered Cord Release in a Patient with Overlapping Symptoms of Charcot-Marie-Tooth Disease

Abstract

Charcot-Marie-Tooth (CMT) disease is the most common inherited neuromuscular disorder causing a symmetric, slowly progressive distal neuropathy of the legs and arms. Tethered cord syndrome (TCS) encompasses a constellation of neurological, gastrointestinal, musculoskeletal, and urinary abnormalities resulting from spinal cord traction. The signs and symptoms of CMT and TCS may be very similar. Electrodiagnostic (EDX) studies are crucial in differentiating between these two conditions. We describe a 20-year-old woman with a history of low back pain, right leg tingling, and difficulty in walking. She experienced bowel and urinary incontinence 11 years earlier as well as back pain, in-toeing gait, and difficulties with balance and coordination. Urodynamic studies and cervical, thoracic, and lumbar magnetic resonance imaging (MRI) were normal, with the latter demonstrating the tip of the conus medullaris in the normal position at the L1-2 interspace and the filum terminale demonstrating no thickening or fatty infiltration. Despite the absence of radiological evidence of TCS, she underwent a tethered cord release (TCR) with improvement of the pain postoperatively. Two years later, the back pain recurred with increasing pain, paresthesia, and weakness of the lower extremities with frequent trip and fall episodes. EDX studies of the lower extremities were requested. Clinical findings included weakness of flexion and extension of the toes as well as dorsiflexors of the ankles bilaterally. The knee and ankle reflexes were absent bilaterally. EDX testing of the lower extremities were non-diagnostic due to loss of sensory and compound muscle action potentials. EDX studies of the upper extremities suggested a demyelinating polyneuropathy, most likely CMT disease. Genetic studies subsequently confirmed CMT type 1A (CMT1A) disease. Ensuing EDX studies on the patient's father and brother also suggested CMT1A disease. Physicians should be aware of the overlapping signs and symptoms of CMT disease and TCS. Performing comprehensive EDX studies prior to a TCR particularly in cases when a lumbar MRI is negative may prove valuable in identifying cases of CMT disease with subsequent confirmation by genetic testing.

Clinical Features of a Newly Described Mutation of Myelin Protein Zero in a Family

“…With a prevalence of one in 2,500 individuals, Charcot-Marie-Tooth (CMT) disease is the most common hereditary neuromuscular disorder marked by progressive distal muscle weakness, sensory loss, decreased or absent deep tendon reflexes (DTRs), and skeletal deformities such as pes cavus [1][2][3][4]. The autosomal dominant 1.5 Mb duplication of the peripheral myelin protein-22 (PMP22) gene on chromosome 17p11.2 is identified in 70-80% of CMT cases (CMT1) [5].…”